The distances of most quasars are much larger than the distances of
galaxies and clusters of galaxies from which superclusters and voids
have been detected in the large-scale structure. Shaver
(180)
discusses the possible existence of very large scale structure in the
three-dimensional distribution of quasars, especially at redshifts
z
0.5. Oort (127,
129)
suggests that the redshift separation between
known superclusters evolved back to z = 2.5 is of the same order as
the separation between the strongest
L absorption systems
observed in quasars (cf.
170a),
which suggests that the absorption systems may be
caused by uncondensed Zel'dovich pancake gas
(215,
215b, and
Section 1.3) that has remained
uncondensed. Detailed analyses of physical
constraints for the gaseous clouds that are the
L absorbers have
been derived by, for example,
Melott (117) and
Ostriker & Ikeuchi
(134),
who discuss alternative models.